This invention relates to a control for an engine and more particularly to a feedback control for the fuel injection system of an engine.
In the interest of fuel economy, better engine performance and overall emissions control, a wide variety of types of feedback control systems have been proposed for controlling the fuel-air ratio of the engine. By appropriately controlling the fuel-air ratio, exhaust emissions can be effectively reduced and fuel economy and engine performance increased.
These types of feedback control systems generally employ a sensor in either the combustion chamber or in the exhaust system that provide a signal indicative of the fuel-air ratio under which the engine is operating. By using this signal, a feedback control controls the air and/or the fuel supply circuits so as to maintain the desired fuel-air ratio. Oxygen sensors are frequently employed for this purpose.
Regardless of the type of sensor employed, the sensors, which are all generally electrical in nature or cooperate with electrical circuits to provide electrical signals for processing, are subject to noise. The noise gives output signals, which may be erratic and not actually indicative of the actual engine conditions.
In order to avoid these problems, which may be particularly acute at certain specific engine running conditions, the ECU or control circuit has been provided with some mechanism whereby the signals are averaged so as to reduce the effect of the noise. However, these systems are not totally effective.
It is, therefore, a principal object of this invention to provide an improved internal combustion engine and control system therefor wherein feedback control can be more accurate.
It is a further object of this invention to provide an internal combustion engine and control therefor wherein the output signal of the fuel-air ratio sensor is filtered under some running conditions to reduce the effect of noise.